Optical apparatus

ABSTRACT

An optical apparatus is disclosed which has a light amount adjusting unit, a lens to be driven by a linear actuator, and a detector for detecting the position of the lens, and which can be reduced in size. The optical apparatus includes a light amount adjusting unit which adjusts a light amount by light shield members translating in a first direction, a vibration type linear actuator which drives the lens in an optical axis direction, a guide member which guides the lens in the optical axis direction, and a detector which detects the position of the lens. When viewed from the optical axis direction of the optical apparatus, the vibration type linear actuator, the guide member, and the detector are arranged along an outer surface of the light amount adjusting unit, the outer surface being provided in a second direction orthogonal to the first direction.

BACKGROUND OF THE INVENTION

The present invention relates to an optical apparatus having a drivingsource for driving a lens in an optical axis direction, andparticularly, to an optical apparatus which includes a vibration orelectromagnetic type linear actuator for use as a driving source.

Some optical apparatuses include an electromagnetic type linear actuatoror a vibration type linear actuator for use as a driving source fordriving a lens (for example, see Japanese Patent Laid-Open No. 8(1996)-179184, Japanese Patent Laid-Open No. 10(1998)-90584, andJapanese Patent Laid-Open No. 2004-046234).

In the optical apparatuses proposed in Japanese Patent Laid-Open No.8(1996)-179184 and Japanese Patent Laid-Open No. 10(1998)-90584 havingthe vibration type linear actuator, each vibration type linear actuatoris formed of a vibrator which produces vibration through anelectromechanical energy conversion action and a contact member which isin press contact with the vibrator. For example, the vibrator is fixedto a lens holding member, the contact member is fixed to a stationarymember of a lens barrel, and the vibrator is caused to produce drivingvibration, thereby moving the lens holding member together with thevibrator.

The vibration type linear actuator is effective in reducing the size ofan optical apparatus since it can generally be provided in a compactsize as compared with the electromagnetic type linear actuator asdisclosed in Japanese Patent Laid-Open No. 2004-046234.

However, the linear actuator disposed away from a light amount adjustingunit (aperture unit) on the outer side thereof as in the opticalapparatus proposed in Japanese Patent Laid-Open No. 8(1996)-179184 leadsto an increased size of the optical apparatus. Especially when such anarrangement is adopted in the optical apparatus which includes a lens tobe driven by the linear actuator on each side of the light amountadjusting unit closer to an object and to an image plane, the opticalapparatus is inevitably increased in size even when the compactvibration linear actuator is used.

In addition, the linear actuator is placed to interfere with the lightamount adjusting unit in an optical axis direction, which makes itdifficult to ensure large space for lens movement.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an optical apparatuswhich has a light amount adjusting unit, a lens to be driven by a linearactuator, and a detector for detecting the position of the lens, andwhich can be reduced in size than conventional optical apparatuses.

According to an aspect, the present invention provides an opticalapparatus including a light amount adjusting unit which adjusts a lightamount by a pair of light shield members translating in a firstdirection orthogonal to an optical axis direction, a lens, a vibrationtype linear actuator which drives the lens in the optical axis directionwith vibration produced through an electromechanical energy conversionaction, a guide member which guides the lens in the optical axisdirection, and the detector which detects the position of the lens. Whenviewed from the optical axis direction of the optical apparatus, thevibration type linear actuator, the guide member, and the detector arearranged along an outer surface of the light amount adjusting unit, theouter surface being provided in a second direction orthogonal to thefirst direction.

According to another aspect, the present invention provides an opticalapparatus including a light amount adjusting unit which adjusts a lightamount by a pair of light shield members translating in a firstdirection orthogonal to an optical axis direction, a first lens disposedcloser to an object than the light amount adjusting unit, a second lensdisposed closer to an image plane than the light amount adjusting unit,a first linear actuator which drives the first lens in the optical axisdirection, a second linear actuator which drives the second lens in theoptical axis direction, a first guide member and a second guide memberwhich guide the first and second lenses in the optical axis direction,respectively, and a first detector and a second detector which detectthe positions of the first and second lenses, respectively. When viewedfrom the optical axis direction of the optical apparatus, the firstlinear actuator, the first guide member, and the first detector arearranged along a first outer surface of the light amount adjusting unit,the first outer surface being provided in a second direction orthogonalto the first direction, and the second linear actuator, the second guidemember, and the second detector are arranged along a second outersurface of the light amount adjusting unit, the second outer surfacebeing provided on the opposite side to the first outer surface.

Other objects and features of the present invention will become readilyapparent from the following description of the preferred embodimentswith reference to accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D show the structure of a lens barrel of an image-takingapparatus which is Embodiment 1 of the present invention when viewedfrom four directions.

FIG. 2 is a section view showing the lens barrel in Embodiment 1 takenalong a plane in parallel with an optical axis.

FIG. 3 is an exploded perspective view of the lens barrel in Embodiment1.

FIG. 4A is a perspective view showing a second lens holding member inthe lens barrel in Embodiment 1.

FIG. 4B is a perspective view showing a first vibration type linearactuator in the lens barrel in Embodiment 1.

FIG. 5A is a perspective view showing a fourth lens holding member inthe lens barrel in Embodiment 1.

FIG. 5B is a perspective view showing a second vibration type linearactuator in the lens barrel in Embodiment 1.

FIG. 5C schematically shows the structure of a light amount adjustingunit in the lens barrel in Embodiment 1.

FIG. 6 is a block diagram showing the electrical structure of theimage-taking apparatus of Embodiment 1.

FIG. 7 is a section view showing a lens barrel in Embodiment 2 of thepresent invention taken along a plane in parallel with an optical axis.

FIG. 8 is a section view showing the lens barrel in Embodiment 2 takenalong a plane perpendicular to the optical axis.

FIG. 9 is a section view showing the lens barrel in Embodiment 2 takenalong a plane perpendicular to the optical axis.

FIG. 10 is an exploded perspective view showing the lens barrel inEmbodiment 2.

FIG. 11 is a section view showing a lens barrel in Embodiment 3 of thepresent invention taken along a plane in parallel with an optical axis.

FIG. 12 is a section view showing the lens barrel in Embodiment 3 takenalong a plane perpendicular to the optical axis.

FIG. 13 is a section view showing the lens barrel in Embodiment 3 takenalong a plane perpendicular to the optical axis.

FIG. 14 is an exploded perspective view showing the lens barrel inEmbodiment 3.

FIGS. 15A to 15D show the structure of a lens barrel of an image-takingapparatus which is Embodiment 4 of the present invention when viewedfrom four directions.

FIG. 16 is a section view showing the lens barrel in Embodiment 4 takenalong a plane in parallel with an optical axis.

FIG. 17 is a section view showing the lens barrel in Embodiment 4 takenalong a plane perpendicular to the optical axis.

FIG. 18 is a section view showing the lens barrel in Embodiment 4 takenalong a plane perpendicular to the optical axis.

FIG. 19 is an exploded perspective view showing the lens barrel inEmbodiment 4.

FIG. 20 is a block diagram showing the electrical structure of theimage-taking apparatus of Embodiment 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will hereinafter bedescribed with reference to the drawings.

Embodiment 1

FIGS. 1A to 1D show a lens barrel, with its exterior removed, in animage-taking apparatus (optical apparatus) which is Embodiment 1 of thepresent invention when viewed from four directions, the front, right,back, and left, respectively. FIG. 2 is a section view of the lensbarrel taken along the plane including the optical axis of the lensbarrel. FIG. 3 is an exploded perspective view of the lens barrel. FIGS.4A and 4B are partial enlarged views showing a vibration type linearactuator for driving a second lens unit which forms part of the lensbarrel. FIGS. 5A and 5B are partial enlarged views showing a vibrationtype linear actuator for driving a fourth lens unit which forms part ofthe lens barrel. FIG. 5C schematically shows the structure of a lightamount adjusting unit which forms part of the lens barrel. FIG. 6 showsthe electrical structure of the image-taking apparatus of Embodiment 1.

In FIGS. 1A to 6, in order from an object side, reference numerals 1shows a fixed first lens unit, 2 the second lens unit which is movablein the optical axis direction for varying magnification, 15 the lightamount adjusting unit, 3 a fixed third lens unit, and 4 the fourth lensunit which is movable in the optical axis direction for correcting imageplane changes associated with varied magnification and for focaladjustment.

Reference numeral 5 shows a rear barrel which holds an image-pickupdevice, later described, and a low pass filter (LPF), and is fixed to acamera body, not shown. Reference numeral 6 shows a first lens holdingmember which holds the first lens unit 1 and is fixed to the rear barrel5 by screws 7, 8, and 9.

Reference numerals 10 and 11 show guide bars (guide members) which areheld substantially in parallel with the optical axis direction by therear barrel 5 and the first lens holding member 6.

Reference numeral 12 shows a second lens holding member which holds thesecond lens unit 2 and to which a mask 32 for cutting unnecessary lightis fixed. The second lens holding member 12 engages with the guide bar10 at an engaging portion 12 a to be guided in the optical axisdirection and engages with the guide bar 11 at an engaging portion 12 bto be prevented from rotation around the guide bar 10. Reference numeral13 shows a third lens holding member which holds the third lens unit 3and is fixed to the rear barrel 5 by a screw 16. Reference numeral 14shows a fourth lens holding member which holds the fourth lens unit 4,and engages with the guide bar 11 at an engaging portion 14 a to beguided in the optical axis direction and engages with the guide bar 10at an engaging portion 14 b to be prevented from rotation around theguide bar 11.

The light amount adjusting unit 15 has an outer shape which is longer ina vertical direction (first direction) than in a horizontal direction(second direction) when viewed from the optical axis direction. Thelight amount adjusting unit 15 is fixed to the rear barrel 5 by a screw17. As shown in FIG. 5C, the light amount adjusting unit 15 is aso-called guillotine type aperture stop in which a pair of apertureblades 15 a and 15 b are substantially translated vertically by a lever15 c rotated by a motor 15 d to increase or reduce the diameter of theaperture. Reference numeral 15 f shows an opening formed by the platesof the light amount adjusting unit 15. The aperture blades 15 a and 15 bare guided vertically by guide pins 15 e provided on the left and right.Unlike a so-called iris type or scissors type, the guillotine typeaperture stop has the horizontal dimension substantially smaller thanthe vertical dimension since the aperture blades 15 a and 15 b aresubstantially translated vertically.

Reference numeral 18 shows a slider (contact member) which is formed ofa magnet and a friction material bonded to each other and is fixed intoa groove 12 c formed in the second lens holding member 12 throughadhesion or the like. Reference numeral 19 shows a vibrator which isformed of an electromechanical energy conversion element and aplate-shaped elastic member on which vibration is produced by theelectromechanical energy conversion element. The elastic member of thevibrator 19 is made of ferromagnet which is attracted by the magnet ofthe slider 18 to bring a press contact surface 18 a of the frictionmaterial of the slider 18 into press contact with press contact surfaces19 a and 19 b formed at two positions in the optical axis direction inthe elastic member of the vibrator 19.

In a first vibration type linear actuator formed of the slider 18 andthe vibrator 19, two frequency signals (pulse signals or alternatesignals) in difference phases are input to the electromechanical energyconversion element through a flexible wiring board 20 to create asubstantially elliptic motion in the press contact surfaces 19 a and 19b of the vibrator 19 to produce driving force in the optical axisdirection in the press contact surface 18 a of the slider 18.

Reference numeral 21 shows a spacer to which the vibrator 19 is fixed,and 22 a plate spring to which the spacer 21 is fixed. The plate spring22 has a shape which is not easily deformed in the in-plane direction ofthe plate and is easily deformed in the direction perpendicular to theplate plane. The plate spring 22 is easily deformed in the rotationdirection around an arbitrary axis included in the plane, and whendeformed, it holds the press contact surfaces 19 a and 19 b of thevibrator 19 in parallel with the press contact surface 18 a of theslider 18. The plate spring 22 not easily deformed in the in-planedirection limits displacement of the vibrator 19 in the optical axisdirection (that is, the driving direction).

Reference numeral 23 shows a vibrator holding member which is fixed tothe first lens holding member 6 by screws 26 and 27 and to which theplate spring 22 is fixed by screws 24 and 25. Reference numeral 28 showsa scale which detects the moving amount (position) of the second lensholding member 12 and is fixed into a groove 12 d formed in the secondlens holding member 12 through adhesion or the like. Reference numeral29 shows a light transmitter/receiver element which applies light to thescale 28 and receives the light reflected by the scale 28 to detect themoving amount of the second lens holding member 12. The lighttransmitter/receiver element 29 and the scale 28 constitute a firstlinear encoder serving as a detector. Reference numeral 30 shows aflexible wiring board which sends and receives a signal to and from thelight transmitter/receiver element 29 and is fixed to the first lensholding member 6 by a screw 31.

As shown in FIG. 1A, the guide bar 10, the first vibration type linearactuator formed of the vibrator 19 and the slider 18, and the firstlinear encoder formed of the light transmitter/receiver element 29 andthe scale 28 are arranged along or close to a planar right side of thelight amount adjusting unit 15 (linear long side on the right whenviewed from the optical axis direction) that is one of the outersurfaces closest to the optical axis position of the light amountadjusting unit 15 of all of the outer surfaces thereof when viewed fromthe front of the optical axis direction. The first vibration type linearactuator and the first linear encoder are disposed vertically next tothe guide bar 10 to sandwich the guide bar 10.

Reference numeral 33 shows a plate spring which is fixed to the fourthlens holding member 14. Reference numeral 34 shows a slider (contactmember) which is formed of a magnet and a friction material bonded toeach other and is fixed to the plate spring 33 through adhesion or thelike. The plate spring 33 has a shape which is not easily deformed inthe in-plane direction of the plate and is easily deformed in thedirection perpendicular to the plate plane. The plate spring 33 iseasily deformed in the rotation direction around an arbitrary axisincluded in the plane, and it holds a press contact surface 34 a of theslider 34 in parallel with press contact surfaces 35 a and 35 b of avibrator 35. The plate spring 33 not easily deformed in the in-planedirection limits displacement of the slider 34 in the optical axisdirection (that is, the driving direction).

The vibrator 35 is formed of an electromechanical energy conversionelement and a plate-shaped elastic member on which vibration is producedby the electromechanical energy conversion element. The elastic memberof the vibrator 35 is made of ferromagnet which is attracted by themagnet of the slider 34 to bring the press contact surface 34 a of thefriction material of the slider 34 into press contact with the presscontact surfaces 35 a and 35 b formed at two positions in the opticalaxis direction in the elastic member of the vibrator 35.

In a second vibration type linear actuator formed of the slider 34 andthe vibrator 35, two frequency signals (pulse signals or alternatesignals) in difference phases are input to the electromechanical energyconversion element through a flexible wiring board 36 to create asubstantially elliptic motion in the press contact surfaces 35 a and 35b of the vibrator 35 b to produce driving force in the optical axisdirection in the press contact surface 34 a of the slider 34.

As shown in FIG. 2, the second lens holding member 12 (engaging portion12 a engaging with the guide bar 10) has a movable range L2 in theoptical axis direction which extends from the object side (the left inFIG. 2) of the light amount adjusting unit 15 toward the image planeside when viewed from the direction perpendicular to the optical axis.The fourth lens holding member 14 (engaging portion 14 a engaging withthe guide bar 11) has a movable range L4 in the optical axis directionwhich extends from the image plane side of the light amount adjustingunit 15 into the light amount adjusting unit 15. In other words, themovable ranges of the second lens holding member 12 and the fourth lensholding member 14 overlap each other in the optical axis direction.Accordingly, the range in which the first vibration type linear actuatoris placed (the range in which the slider 18 is provided) and the rangein which the second vibration type linear actuator is placed (the rangein which the slider 34 is provided) overlap each other in the opticalaxis direction.

Reference numeral 37 shows a spacer to which the vibrator 35 is fixed,and 38 a plate spring to which the spacer 37 is fixed. The plate spring38 has a shape which is not easily deformed in the in-plane direction ofthe plate and is easily deformed in the direction perpendicular to theplate plane. The plate spring 38 is easily deformed in the rotationdirection around an arbitrary axis included in the plane, and it holdsthe press contact surfaces 35 a and 35 b of the vibrator 35 in parallelwith the press contact surface 34 a of the slider 34. The plate spring38 not easily deformed in the in-plane direction limits displacement ofthe vibrator 35 in the optical axis direction (that is, the drivingdirection).

Reference numeral 39 shows a vibrator holding member which is fixed tothe rear barrel 5 by screws 42 and 43 and to which the plate spring 38is fixed by screws 46 and 47.

Reference numeral 48 shows a scale which detects the moving amount(position) of the fourth lens holding member 14 and is fixed into agroove 14 d formed in the fourth lens holding member 14 through adhesionor the like. Reference numeral 49 shows a light transmitter/receiverelement which applies light to the scale 48 and receives the lightreflected by the scale 48 to detect the moving amount of the fourth lensholding member 14. The light transmitter/receiver element 49 and thescale 48 constitute a second linear encoder serving as a detector.Reference numeral 50 shows a flexible wiring board which sends andreceives a signal to and from the light transmitter/receiver element 49and is fixed to the rear barrel 5 by a screw 51.

As shown in FIG. 1A, the guide bar 11, the second vibration type linearactuator formed of the vibrator 35 and the slider 34, and the secondlinear encoder formed of the light transmitter/receiver element 49 andthe scale 48 are arranged along or close to a planar left side of thelight amount adjusting unit 15 (linear long side on the left when viewedfrom the optical axis direction) that is the other outer surface closestto the optical axis position of the light amount adjusting unit 15 ofall of the outer surfaces thereof when viewed from the front of theoptical axis direction. The second vibration type linear actuator andthe second linear encoder are disposed vertically next to the guide bar11 to sandwich the guide bar 11.

The set of the first vibration type linear actuator, the guide bar 10,and the first linear encoder, and the set of the second vibration typelinear actuator, the guide bar 11, and the second linear encoder arearranged substantially symmetrically with respect to an axis extendingvertically through the center of the optical axis.

In FIG. 6, reference numeral 101 shows the image-pickup device formed ofa CCD sensor, a CMOS sensor or the like. Reference numeral 102 shows thefirst vibration type linear actuator which includes the slider 18 andthe vibrator 19, and serves as a driving source of the second lens unit2 (second lens holding member 12). Reference numeral 103 shows thesecond vibration type linear actuator which includes the slier 34 andthe vibrator 35, and serves as a driving source of the fourth lens unit4 (fourth lens holding member 14).

Reference numeral 104 shows the motor which serves as a driving sourceof the light amount adjusting unit 15. Reference numeral 105 shows asecond lens encoder realized by the first linear encoder which includesthe scale 28 and the light transmitter/receiver element 29, 106 a fourthlens encoder realized by the second linear encoder which includes thescale 48 and the light transmitter/receiver element 49. These encodersdetect the relative positions (moving amounts from a reference position)of the second lens unit 2 and the fourth lens unit 4 in the optical axisdirection, respectively. While Embodiment 1 employs optical encoders asthe encoders, it is possible to use a magnetic encoder or an encoderwhich detects an absolute position by using electrical resistance.

Reference numeral 107 shows an aperture encoder which is, for example,of the type in which a hall element is provided within the motor 104 asthe driving source of the light amount adjusting unit 15 and is used todetect a rotational position relationship between a rotor and a statorof the motor 104.

Reference numeral 117 shows a CPU serving as a controller responsiblefor control of operation of the image-taking apparatus. Referencenumeral 108 shows a camera signal processing circuit which performsamplification, gamma correction or the like on the output from theimage-pickup device 101. After the predetermined processing, a contrastsignal of a video signal is transmitted through an AE gate 109 and an AFgate 110. The gates 109 and 110 set an optimal range in the entirescreen for extracting the signal for exposure setting and focusing.These gates 109 and 110 may have variable sizes, or a plurality of gates109 and 110 may be provided.

Reference numeral 114 shows an AF (auto-focus) signal processing circuitfor auto-focus which extracts a high-frequency component of the videosignal to produce an AF evaluation value signal. Reference numeral 115shows a zoom switch for zooming operation. Reference numeral 116 shows azoom tracking memory which stores information about target positions towhich the fourth lens unit 4 is to be driven in accordance with thecamera-to-object distance and the position of the second lens unit 2 inorder to maintain an in-focus state in varying magnification. Memory inthe CPU 117 may be used as the zoom tracking memory.

In the abovementioned structure, when a user operates the zoom switch115, the CPU 117 controls the first vibration type linear actuator 102for driving the second lens unit 2 and calculates the target drivingposition of the fourth lens unit 4 based on the information in the firstzoom tracking memory 116 and the current position of the second lensunit 2 determined from the detection result of the second lens unitencoder 105 to control the second vibration type linear actuator 103 fordriving of the fourth lens unit 4 to that target driving position.Whether or not the fourth lens unit 4 has reached the target drivingposition is determined by the matching of the current position of thefourth lens unit 4 determined from the detection result of the fourthlens unit encoder 106 with the target driving position.

In the auto-focus, the CPU 117 controls the second vibration type linearactuator 103 to drive the fourth lens unit 4 to search for the positionwhere the AF evaluation value determined by the AF signal processingcircuit 114 is at the peak.

To provide appropriate exposure, the CPU 117 controls the motor 104 ofthe light amount adjusting unit 15 to increase or reduce the aperturediameter such that the average value of the luminance signal through theAE gate 109 is equal to a predetermined value, that is, such that theoutput from the aperture encoder 107 has a value corresponding to thepredetermined value.

In the abovementioned structure, the slider 18 is formed by using themagnet which attracts the vibrator 19 to provide the press contact forcenecessary for producing the driving force as the vibration type linearactuator. Thus, any reaction force of the press contact force does notact on the second lens holding member 12. As a result, the frictionalforce produced at the engaging portions 12 a and 12 b of the second lensholding member 12 engaging with the guide bars 10 and 11 is notincreased, and the driving load due to the friction is not increased. Inaddition, the plate spring 22 produces small force, so that the forceacting from the plate spring 22 on the engaging portions 12 a and 12 bengaging with the guide bars 10 and 11 is small and hardly increases thefrictional force produced at the engaging portions 12 a and 12 b. Thisenables the use of the low-power and small vibration type linearactuator, resulting in a reduction in size of the lens barrel.

Since large press contact force does not act on the second lens holdingmember 12, the frictional force produced at the engaging portions 12 aand 12 b of the second lens holding member 12 engaging with the guidebars 10 and 11 is not increased. The power or size of the firstvibration type linear actuator 102 does not need to be increased, andthe wear (abrasion) due to the friction between the guide bars 10, 11and the engaging portions 12 a, 12 b can be reduced. Also, the finedriving of the second lens holding member 12 (second lens unit 2) can beaccurately achieved.

Even when a manufacturing error or the like changes the position of anypress contact surface with respect to an axis in parallel with theoptical axis or the inclination around that axis in the optical axisdirection, the plate spring 22 is deformed to change the position orinclination (orientation) of the vibrator 19 to maintain both of thepress contact surfaces in parallel with each other, thereby holding anappropriate contact state between the surfaces. The plate spring 22 hasa spring constant set such that it is deformed in response to a smallerforce than the abovementioned press contact force. The press contactforce is not changed greatly even when the position or inclination ofany press contact surface is changed. Consequently, it is possible toprovide stably an output consistent with the performance inherent in thefirst vibration type linear actuator 102.

On the other hand, the slider 34 is formed by using the magnet whichattracts the vibrator 35 to provide the press contact force necessaryfor producing the driving force as the vibration type linear actuator.Thus, any reaction force of the press contact force does not act on thefourth lens holding member 14. As a result, the frictional forceproduced at the engaging portions 14 a and 14 b of the fourth lensholding member 14 engaging with the guide bars 11 and 10 is notincreased, and the driving load due to the friction is not increased. Inaddition, the plate springs 33 and 38 produce small force, so that theforce acting from the plate springs 33 and 38 on the engaging portions14 a and 14 b engaging with the guide bars 11 and 10 is small and hardlyincreases the frictional force produced at the engaging portions 14 aand 14 b. This enables the use of the low-power and small vibration typelinear actuator, resulting in a reduction in size of the lens barrel.

Since large press contact force does not act on the fourth lens holdingmember 14, the frictional force produced at the engaging portions 14 aand 14 b of the fourth lens holding member 14 engaging with the guidebars 11 and 10 is not increased. The power or size of the secondvibration type linear actuator 103 does not need to be increased, andthe wear due to the friction between the guide bars 10, 11 and theengaging portions 14 a, 14 b can be reduced. Also, the fine driving ofthe fourth lens holding member 14 (fourth lens unit 4) can be accuratelyachieved.

Even when a manufacturing error or the like changes the position of anypress contact surface with respect to an axis in parallel with theoptical axis or the inclination around that axis in the optical axisdirection, the plate springs 33 and 38 are deformed to change theposition or inclination (orientation) of the vibrator 34 to maintainboth of the press contact surfaces in parallel with each other, therebyholding an appropriate contact state between the surfaces. Each of theplate springs 33 and 38 has a spring constant set such that it isdeformed in response to a smaller force than the abovementioned presscontact force. The press contact force is not changed greatly even whenthe position or inclination of any press contact surface is changed.Consequently, it is possible to provide stably an output consistent withthe performance inherent in the second vibration type linear actuator103.

As described above, in Embodiment 1, the guide bar 10, the firstvibration type linear actuator, and the first linear encoder arearranged along (close to) the right side which is one of the flatsurfaces of the light amount adjusting unit 15 closest to the opticalaxis when viewed from the optical axis direction. The first vibrationtype linear actuator and the first linear encoder are disposed next tothe guide bar 10 below and above, respectively. In addition, the guidebar 11, the second vibration type linear actuator, and the second linearencoder are arranged along (close to) the left side which is one of theflat surfaces of the light amount adjusting unit 15 closest to theoptical axis when viewed from the optical axis direction. The secondvibration type linear actuator and the second linear encoder aredisposed next to the guide bar 11 below and above, respectively.

Thus, although the optical apparatus has the light amount adjusting unit15, the two vibration type linear actuators for driving the second andfourth lens holding members 12 and 14 (second and fourth lens units 2and 4) disposed on the object side and the image plane side of the lightamount adjusting unit 15, the two guide bars 10 and 11 for guiding thelens holding members 12 and 14 in the optical axis direction, and thetwo linear encoders for detecting the positions of the lens holdingmembers 12 and 14, it can be formed in a compact size.

Since the sliders 18 and 34 are disposed next to the guide bars 10 and11, respectively, the second and fourth lens holding members 12 and 14can be driven smoothly. In addition, the scales 28 and 48 disposed nextto the guide bars 10 and 11 reduce displacement of the scales 28 and 48due to backlash of the engaging portions 12 a, 12 b and 14 a, 14 b ofthe second and forth lens holding members 12 and 14 engaging with theguide bars 10 and 11 to enable accurate detection of positions.

When the linear actuator and the linear encoder are disposed across theoptical axis from the guide bar for guiding the lens holding memberwhich is driven and whose position is detected by them, the linearencoder may be moved in the direction opposite to the driving directionwith the guide bar as the supporting point at the start of the drivingdue to backlash at the engaging portion of the lens holding memberengaging with the guide bar. This may reduce the accuracy of theposition detection. In Embodiment 1, however, the linear actuator andthe linear encoder are disposed on the same side as the guide bar forguiding the lens holding member which is driven and whose position isdetected by them, so that such a problem does not arise and the positioncan be detected accurately.

Embodiment 2

FIG. 7 shows a section view of a lens barrel of an image-takingapparatus which is Embodiment 2 of the present invention taken along aplane in parallel with an optical axis and perpendicular to a presscontact surface between a slider and a vibrator of a vibration typelinear actuator. FIG. 8 shows a section view of the lens barrel inEmbodiment 2 taken along a plane perpendicular to the optical axis andperpendicular to a press contact surface of a vibration type linearactuator for driving a second lens unit when viewed from an object side.FIG. 9 shows a section view of the lens barrel in Embodiment 2 takenalong a plane perpendicular to the optical axis and perpendicular to apress contact surface of a vibration type linear actuator for driving afourth lens unit when viewed from the object side. FIG. 10 is anexploded view showing the lens barrel in Embodiment 2. The image-takingapparatus of Embodiment 2 has the same electrical structure as that inEmbodiment 1.

In FIGS. 7 to 10, in order from the object side, reference numeral 201shows a fixed first lens unit, 202 the second lens unit which is movablein the optical axis direction for varying magnification, 215 a lightamount adjusting unit, 203 a fixed third lens unit, and 204 the fourthlens unit which is movable in the optical axis direction for correctingimage plane changes associated with varied magnification and for focaladjustment.

Reference numeral 205 shows a rear barrel which holds an image-pickupdevice and a low pass filter (LPF), and is fixed to a camera body, notshown. Reference numeral 206 shows a first lens holding member whichholds the first lens unit 201 and is fixed to the rear barrel 205 byscrews 207, 208, and 209.

Reference numerals 210 and 211 show guide bars (guide members) which areheld substantially in parallel with the optical axis direction by therear barrel 205 and the first lens holding member 206.

Reference numeral 212 shows a second lens holding member which holds thesecond lens unit 202 and to which a mask 232 for cutting unnecessarylight is fixed. The second lens holding member 212 engages with theguide bar 210 at an engaging portion 212 a to be guided in the opticalaxis direction and engages with the guide bar 211 at an engaging portion212 b to be prevented from rotation around the guide bar 210. Referencenumeral 213 shows a third lens holding member which holds the third lensunit 203 and is fixed to the rear barrel 205 by a screw 216. Referencenumeral 214 shows a fourth lens holding member which holds the fourthlens unit 204, and engages with the guide bar 211 at an engaging portion214 a to be guided in the optical axis direction and engages with theguide bar 210 at an engaging portion 214 b to be prevented from rotationaround the guide bar 211.

The light amount adjusting unit 215 has an outer shape which is longerin a vertical direction (first direction) than in a horizontal direction(second direction) when viewed from the optical axis direction. Thelight amount adjusting unit 215 is fixed to the rear barrel 205 by ascrew 217. The light amount adjusting unit 215 has the same structure asthat in Embodiment 1 shown in FIG. 5C.

Reference numeral 218 shows a slider which is formed of a frictionmaterial. Reference numeral 219 shows a vibrator which is formed of anelectromechanical energy conversion element and a plate-shaped elasticmember on which vibration is produced by the electromechanical energyconversion element. Reference numeral 220 shows a flexible wiring boardwhich is connected to the vibrator 219 and transmits a signal to theelectromechanical energy conversion element. The flexible wiring board220 has a bend portion (deformation portion) 220 a which is deformed asthe second lens holding member 212 is moved in the optical axisdirection.

In a first vibration type linear actuator formed of the slider 218 andthe vibrator 219, while the slider 218 is in press contact with thevibrator 219, two frequency signals (pulse signals or alternate signals)in difference phases are input to the electromechanical energyconversion element through the flexible wiring board 220 to create asubstantially elliptic motion in press contact surfaces 219 a (formed attwo positions in the optical axis direction as in Embodiment 1) of thevibrator 219 to produce driving force in the optical axis direction in apress contact surface 218 a of the slider 218.

Reference numeral 221 shows a spacer which fixes the vibrator 219 andhas a hole 221 a formed in its center. A spherical projection 212 eformed on the second lens holding member 212 is fitted into the hole 221a to hold the spacer 221 such that its movement is prevented (limited)in the optical axis direction (that is, the driving direction) and itsrotation and movement in a direction other than the optical axisdirection are permitted. The outer periphery of the spacer 221 is heldwith some backlash by projections 212 c, 212 d, and a projection, notshown, formed on the second lens holding member 212. This enables thespacer 221 to be moved such that the press contact surfaces 219 a of thevibrator 219 is in parallel with the press contact surface 218 a of theslider 218.

Reference numeral 222 shows a press contact bar which retains thesurface of the slider 218 opposite to the press contact surface 218 a,224 a coil spring which is hung from a projection 221 b of the spacer221 to the press contact bar 222, and 225 a coil spring which is hungfrom a projection 221 c of the spacer 221 to the press contact bar 222.The press contact bar 222 and the spacer 221 pull each other through thepull force of the coil springs 224 and 225. The slider 218 retained bythe press contact bar 222 and the vibrator 219 fixed to the spacer 221are held such that their press contact surfaces 218 a and 219 a are inpress contact with each other.

Reference numeral 223 shows a slider holding member having a holdingportion 223 a to which the slider 218 is fixed through adhesion or thelike. The slider 223 is fixed to the first lens holding member 206 byscrews 226 and 227.

Reference numeral 228 shows a scale which detects the position of thesecond lens holding member 212 and is fixed into a groove 212 f formedin the second lens holding member 212 through adhesion or the like.Reference numeral 229 shows a light transmitter/receiver element whichapplies light to the scale 228 and receives the light reflected by thescale 228 to detect the moving amount of the second lens holding member212. The scale 228 and the light transmitter/receiver element 229constitute a first linear encoder serving as a detector.

Reference numeral 230 shows a flexible wiring board which sends andreceives a signal to and from the light transmitter/receiver element 229and is fixed to the first lens holding member 206 by a screw 231.

As shown in FIG. 8, the guide bar 210, the first vibration type linearactuator formed of the vibrator 219 and the slider 218, and the firstlinear encoder formed of the light transmitter/receiver element 229 andthe scale 228 are arranged along or close to a planar left side of thelight amount adjusting unit 215 (linear long side on the left whenviewed from the optical axis direction) that is one of the outersurfaces closest to the optical axis position of the light amountadjusting unit 215 of all of the outer surfaces thereof when viewed fromthe front of the optical axis direction. The first vibration type linearactuator and the first linear encoder are disposed vertically next tothe guide bar 210 to sandwich the guide bar 210.

Reference numeral 233 shows a press contact bar, 240 and 241 coilsprings whose ends are hung on the press contact bar 233. Referencenumeral 234 shows a slider which is made of a friction material retainedby the press contact bar 233 and is fixed to a groove 214 e of thefourth lens holding member 214.

Reference numeral 235 shows a vibrator which is formed of anelectromechanical energy conversion element and a plate-shaped elasticmember on which vibration is produced by the electromechanical energyconversion element. Reference numeral 236 shows a flexible wiring boardwhich is connected to the electromechanical energy conversion element ofthe vibrator 235. In a second vibration type linear actuator formed ofthe slider 234 and the vibrator 235, while the slider 234 is in presscontact with the vibrator 235, two frequency signals (pulse signals oralternate signals) in difference phases are input to theelectromechanical energy conversion element through the flexible wiringboard 236 to create a substantially elliptic motion in press contactsurfaces 235 a (formed at two positions in the optical axis direction asin Embodiment 1) of the vibrator 235 to produce driving force in theoptical axis direction in a press contact surface 234 a of the slider234.

As shown in FIG. 7, the range in which the first vibration type linearactuator is placed in the optical axis direction (the range in which theslider 218 is placed) and a movable range L2 of the second lens holdingmember 212 in the optical axis direction extend from the object side(the left in FIG. 7) of the light amount adjusting unit 215 toward theimage plane side. On the other hand, the range in which the secondvibration type linear actuator is placed in the optical axis direction(the range in which the slider 234 is placed) and a movable range L4 ofthe fourth lens holding member 214 in the optical axis direction extendfrom the image plane side of the light amount adjusting unit 215 towardthe object side. In other words, the ranges in which the first andsecond vibration type linear actuators are placed (the movable ranges ofthe second and fourth lens holding members 212 and 214) overlap eachother in the optical axis direction.

Reference numeral 237 shows a spacer which holds the vibrator 235 andhas projections 237 b and 237 c on which the other ends of the coilsprings 240 and 241 are hung. The coil springs 240 and 241 pull thepress contact bar 233 and the spacer 237, the press contact bar 233pushes the slider 234, and the spacer 237 pushes the vibrator 235, sothat the press contact surface 234 a of the slider 234 is in presscontact with the press contact surfaces 235 a of the vibrator 235.

Reference numeral 239 shows a vibrator holding member which holds thevibrator 235. The vibrator holding member 239 has shafts 239 a and 239 bwhich extend toward the object side and the image plane side androtatably engage with bearings 205 a and 205 b of the rear barrel 205,respectively. A spherical projection 239 c formed on the inner side ofthe vibrator holding member 239 is fitted into a conical hole 237 aformed in the spacer 237. The vibrator holding member 239 is biasedtoward the object by a torsion coil spring 238 disposed on the shaft 239b and thus is held without backlash in the optical axis direction. Thevibrator holding member 239 is urged toward the inward rotationdirection around the shafts 239 a and 239 b by the torsion coil spring238, which presses the spherical projection 239 c into the hole 237 a.The spacer 237 and the vibrator 235 held thereby are kept such thattheir movement is prevented (limited) in the optical axis direction(that is, the driving direction) and their rotation around the sphericalprojection 239 c and their movement in the direction substantiallyperpendicular to the press contact surface 235 a are permitted.

Reference numeral 248 shows a scale which detects the position of thefourth lens holding member 214 and is fixed into a groove 214 d formedin the fourth lens holding member 214 through adhesion or the like.Reference numeral 249 shows a light transmitter/receiver element whichapplies light to the scale 248 and receives the light reflected by thescale 248 to detect the moving amount of the fourth lens holding member214. The scale 248 and the light transmitter/receiver element 249constitute a second linear encoder serving as a detector.

Reference numeral 250 shows a flexible wiring board which sends andreceives a signal to and from the light transmitter/receiver element 249and is fixed to the rear barrel 205 by a screw 251.

As shown in FIG. 9, the guide bar 211, the second vibration type linearactuator formed of the vibrator 235 and the slider 234, and the secondlinear encoder formed of the light transmitter/receiver element 249 andthe scale 248 are arranged along or close to a planar right side of thelight amount adjusting unit 215 (linear long side on the right whenviewed from the optical axis direction) that is one of the outersurfaces closest to the optical axis position of the light amountadjusting unit 215 of all of the outer surfaces thereof when viewed fromthe front of the optical axis direction. The second vibration typelinear actuator and the second linear encoder are disposed verticallynext to the guide bar 211 to sandwich the guide bar 211.

The set of the first vibration type linear actuator, the guide bar 210,and the first linear encoder, and the set of the second vibration typelinear actuator, the guide bar 211, and the second linear encoder arearranged substantially symmetrically with respect to an axis extendingvertically through the center of the optical axis.

In the abovementioned structure, the coil springs 224 and 225 pull thepress contact bar 222 and the spacer 221 to press the slider 218 againstthe vibrator 219 to provide the press contact force necessary forproducing the driving force as the vibration type linear actuator. Thus,any reaction force of the press contact force does not act on the secondlens holding member 212. As a result, the frictional force produced atthe engaging portions 212 a and 212 b of the second lens holding member212 engaging with the guide bars 210 and 211 is not increased and thedriving load due to the friction is not increased.

The slider 218 is fixed to the slider holding member 223. On other hand,the spacer 221 engages with the spherical projection 212 e of the secondlens holding member 212 and transmits the force necessary for drivingthe second lens holding member 212 without backlash in the optical axisdirection, but transmits only small force in the moving direction otherthan the driving direction and in the rotation direction. Thus, anypress contact force does not act on the second lens holding member 212.

This enables the use of the low-power and small vibration type linearactuator, resulting in a reduction in size of the lens barrel.

In addition, the hole 221 a of the spacer 221 for holding the vibrator219 receives the spherical projection 212 e of the second lens holdingmember 212 to hold the second lens holding member 212 to allow therotation around the spherical projection 212 e and the movement in thedirection other than the optical axis direction. Even when amanufacturing error or the like changes the position or inclination ofany press contact surface in the optical axis direction, the position orinclination (orientation) of the vibrator 219 is changed to maintainboth of the press contact surfaces in parallel with each other, therebyholding an appropriate contact state between the surfaces. The presscontact force is not changed greatly even when the position orinclination of the spacer 221 is changed. Consequently, it is possibleto provide stably an output consistent with the performance inherent inthe first vibration type linear actuator 102.

Since large press contact force does not act on the second lens holdingmember 212, the frictional force produced at the engaging portions 212 aand 212 b of the second lens holding member 212 engaging with the guidebars 210 and 211 is not increased. The power or size of the firstvibration type linear actuator does not need to be increased, and thewear due to the friction between the guide bars 210, 211 and theengaging portions 212 a, 212 b can be reduced. Also, the fine driving ofthe second lens holding member 212 (second lens unit 202) can beaccurately achieved.

On the other hand, the coil springs 240 and 241 pull the press contactbar 233 and the spacer 237 to press the slider 234 against the vibrator235 to provide the press contact force necessary for producing thedriving force as the vibration type linear actuator. Thus, any reactionforce of the press contact force does not act on the fourth lens holdingmember 214. As a result, the frictional force produced at the engagingportions 214 a and 214 b of the fourth lens holding member 214 engagingwith the guide bars 211 and 210 is not increased and the driving loaddue to the friction is not increased.

The slider 234 is fixed into the groove 214 e of the fourth lens holdingmember 214. The conical hole 237 a of the spacer 237 receives thespherical projection 239 c of the vibrator holding member 239, so thatonly retaining force for supporting the spacer 237 without backlash actson the spacer 237. Since the retaining force for supporting the spacer237 without backlash is smaller than the abovementioned press contactforce, the frictional force produced at the engaging portions 214 a and214 b of the fourth lens holding member 214 engaging with the guide bars211 and 210 is hardly increased, and the driving load due to thefriction is hardly increased.

This enables the use of the low-power and small vibration type linearactuator, resulting in a reduction in size of the lens barrel.

As described above, the press contact surface 234 a of the slider 234 isin press contact with the press contact surfaces 235 a of the vibrator235 by the pull force of the coil springs 240 and 241, and the sphericalprojection 239 c of the vibrator holding member 239 is pressed into theconical hole 237 a to engage without backlash by the biasing force ofthe coil spring 238. This enables the vibrator 235 to rotate around thespherical projection 239 c. The vibrator holding member 239 is rotatedaround the shafts 239 a and 239 b to allow the vibrator 235 to be movedin the direction substantially perpendicular to the press contactsurfaces 235 a or inclined to rotate around the spherical projection 239c. Even when a manufacturing error or the like changes the position ofany press contact surface with respect to an axis in parallel with theoptical axis or the inclination around that axis in the optical axisdirection, the position or inclination (orientation) of the vibrator 235is changed to maintain both of the press contact surfaces in parallelwith each other, thereby holding an appropriate contact state betweenthe surfaces.

The coil spring 238 may produce only enough force to cause the sphericalprojection 239 c of the vibrator holding member 239 to engage with theconical hole 237 a of the spacer 237 without backlash, and the force maybe smaller than the force for bringing the slider 234 into press contactwith the vibrator 235 to produce the driving force. Thus, the presscontact force is not substantially changed even when the position of thepress contact surface is changed.

Consequently, it is possible to provide stably an output consistent withthe performance inherent in the second vibration type linear actuator.

Since large press contact force does not act on the fourth lens holdingmember 214, the frictional force produced at the engaging portions 214 aand 214 b of the fourth lens holding member 214 engaging with the guidebars 211 and 210 is not increased. The power or size of the secondvibration type linear actuator does not need to be increased, and thewear due to the friction between the guide bars 211, 210 and theengaging portions 214 a, 214 b can be reduced. Also, the fine driving ofthe fourth lens holding member 214 (second lens unit 204) can beaccurately achieved.

When the lens holding member is moved by a large amount, the sliderneeds to have a great length. To allow the movement of that long sliderin the optical axis direction, long space for the slider movement needsto be ensured in the optical axis direction.

In Embodiment 2, however, in the first vibration type linear actuatorfor driving the second lens holding member 212 which is moved by alarger amount as compared with the fourth lens holding member 214, theslider 218 having a greater length in the optical axis direction thanthat of the slider 234 of the second vibration type linear actuator isfixed, while the vibrator 219 is moved together with the second lensholding member 212 in the optical axis direction. Since the long slider218 is not moved in the optical axis direction in this manner, only theshort space may be required for placing the first vibration type linearactuator in the optical axis direction, which enables a reduction insize of the lens barrel.

In Embodiment 2, in the second vibration type linear actuator fordriving the fourth lens holding member 214 which is moved by a smalleramount as compared with the second lens holding member 212, the slider234 is fixed to the fourth lens holding member 214 and is moved in theoptical axis direction, while the vibrator 235 is fixed and is not movedin the optical axis direction. Thus, the flexible wiring board 250 doesnot need to have any deformation portion, so that the flexible wiringboard 250 can be easily handled to enhance the flexibility in design.This also allows a reduction in size of the lens barrel.

As described above, in Embodiment 2, the guide bar 210, the firstvibration type linear actuator, and the first linear encoder arearranged along (close to) the left side which is one of the flatsurfaces of the light amount adjusting unit 215 closest to the opticalaxis when viewed from the optical axis direction. The first vibrationtype linear actuator and the first linear encoder are disposed next tothe guide bar 210 above and below, respectively.

In addition, the guide bar 211, the second vibration type linearactuator, and the second linear encoder are arranged along (close to)the right side which is one of the flat surfaces of the light amountadjusting unit 215 closest to the optical axis when viewed from theoptical axis direction. The second vibration type linear actuator andthe second linear encoder are disposed next to the guide bar 211 aboveand below, respectively.

Thus, although the optical apparatus has the light amount adjusting unit215, the two vibration type linear actuators for driving the second andfourth lens holding members 212 and 214 (second and fourth lens units202 and 204) disposed on the object side and the image plane side of thelight amount adjusting unit 215, the two guide bars 210 and 211 forguiding the lens holding members 212 and 214 in the optical axisdirection, and the two linear encoders for detecting the positions ofthe lens holding members 212 and 214, it can be formed in a compactsize.

Since the sliders 218 and 234 are disposed next to the guide bars 210and 211, the second and fourth lens holding members 212 and 214 can bedriven smoothly. In addition, the scales 228 and 248 disposed next tothe guide bars 210 and 211 reduce displacement of the scales 228 and 248due to backlash of the engaging portions 212 a, 212 b and 214 a, 214 bof the second and forth lens holding members 212 and 214 engaging withthe guide bars 210 and 211 to enable accurate detection of positions.

When the linear actuator and the linear encoder are disposed across theoptical axis from the guide bar for guiding the lens holding memberwhich is driven and whose position is detected by them, the linearencoder may be moved in the direction opposite to the driving directionwith the guide bar as the supporting point at the start of the drivingdue to backlash at the engaging portion of the lens holding memberengaging with the guide bar. This may reduce the accuracy of theposition detection. In Embodiment 2, however, the linear actuator andthe linear encoder are disposed on the same side as the guide bar forguiding the lens holding member which is driven and whose position isdetected by them, so that such a problem does not arise and the positioncan be detected accurately.

Embodiment 3

FIGS. 11 to 14 show the structure of a lens barrel of an image-takingapparatus which is Embodiment 3 of the present invention. FIG. 11 showsa section view of the lens barrel in Embodiment 3 taken along a plane inparallel with an optical axis and perpendicular to a press contactsurface between a slider and vibrator of a vibration type linearactuator. FIG. 12 shows a section view of the lens barrel in Embodiment3 taken along a plane perpendicular to the optical axis andperpendicular to a press contact surface of a vibration type linearactuator for driving a second lens unit when viewed from an object side.FIG. 13 shows a section view of the lens barrel in Embodiment 3 takenalong a plane perpendicular to the optical axis and perpendicular to apress contact surface of a vibration type linear actuator for driving afourth lens unit when viewed from the object side. FIG. 14 is anexploded view showing the lens barrel in Embodiment 3. The image-takingapparatus of Embodiment 3 has the same electrical structure as that inEmbodiment 1.

In FIGS. 11 to 14, in order from the object side, reference numeral 301shows a fixed first lens unit, 302 the second lens unit which is movablein the optical axis direction for varying magnification, 315 a lightamount adjusting unit, 303 a fixed third lens unit, and 304 the fourthlens unit which is movable in the optical axis direction for correctingimage plane changes associated with varied magnification and for focaladjustment.

Reference numeral 305 shows a rear barrel which holds an image-pickupdevice, later described, and a low pass filter (LPF), and is fixed to acamera body, not shown. Reference numeral 306 shows a first lens holdingmember which holds the first lens unit 301 and is fixed to the rearbarrel 305 by screws 307, 308, and 309.

Reference numerals 310 and 311 show guide bars (guide members) which areheld substantially in parallel with the optical axis direction by therear barrel 305 and the first lens holding member 306.

Reference numeral 312 shows a second lens holding member which holds thesecond lens unit 302 and to which a mask 332 for cutting unnecessarylight is fixed. The second lens holding member 312 engages with theguide bar 310 at an engaging portion 312 a to be guided in the opticalaxis direction and engages with the guide bar 311 at an engaging portion312 b to be prevented from rotation around the guide bar 310. Referencenumeral 313 shows a third lens holding member which holds the third lensunit 303 and is fixed to the rear barrel 305 by a screw 316. Referencenumeral 314 shows a fourth lens holding member which holds the fourthlens unit 304, and engages with the guide bar 311 at an engaging portion314 a to be guided in the optical axis direction and engages with theguide bar 310 at an engaging portion 314 b to be prevented from rotationaround the guide bar 311.

The light amount adjusting unit 315 has an outer shape which is longerin a vertical direction (first direction) than in a horizontal direction(second direction) when viewed from the optical axis direction. Thelight amount adjusting unit 315 is fixed to the rear barrel 305 by ascrew 317. The light amount adjusting unit 215 has the same structure asthat in Embodiment 1 shown in FIG. 5C.

Reference numeral 318 shows a slider which is formed of a magnet and afriction material bonded to each other. Reference numeral 319 shows avibrator which is formed of an electromechanical energy conversionelement and a plate-shaped elastic member on which vibration is producedby the electromechanical energy conversion element. The elastic memberof the vibrator 319 is made of ferromagnet which is attracted by themagnet of the slider 318 to bring an press contact surface 318 a of thefriction material of the slider 318 into press contact with presscontact surfaces 319 a (formed at two positions in the optical axisdirection as in Embodiment 1) of the elastic member of the vibrator 319.

Reference numeral 320 shows a flexible wiring board which is connectedto the vibrator 319 and transmits a signal to the electromechanicalenergy conversion element. The flexible wiring board 320 has a bendportion (deformation portion) 320 a which is deformed as the second lensholding member 312 is moved in the optical axis direction.

In a first vibration type linear actuator formed of the slider 318 andthe vibrator 319, while the slier 318 is in press contact with thevibrator 319, two frequency signals (pulse signals or alternate signals)in difference phases are input to the electromechanical energyconversion element through the flexible wiring board 320 to create asubstantially elliptic motion in the press contact surfaces 319 a of thevibrator 319 to produce driving force in the optical axis direction inthe press contact surface 318 a of the slider 318.

Reference numeral 321 shows a spacer which fixes the vibrator 319, 322 aplate spring which fixes the spacer 321. The plate spring 322 has ashape which is not easily deformed in the in-plane direction, is easilydeformed in the direction perpendicular to the plane, and is easilydeformed in the rotation direction around an arbitrary axis included inthe plane. The plate spring 322 not easily deformed in the in-planedirection limits displacement of the vibrator 319 in the optical axisdirection (that is, the driving direction).

Reference numerals 324 and 325 show screws which secure the plate spring322 to the second lens holding member 312. Reference numeral 323 shows avibrator frame to which the slider 318 is fixed through adhesion or thelike. The vibrator frame 323 is fixed to the first lens holding member306 by screws 326 and 327.

Reference numeral 328 shows a scale which detects the position of thesecond lens holding member 312 and is fixed into a square hole 312 d ofthe second lens holding member 312 through adhesion or the like.

Reference numeral 329 shows a light transmitter/receiver element whichapplies light to the scale 328 and receives the light reflected by thescale 28 to detect the moving amount of the second lens holding member312. The scale 328 and the light transmitter/receiver element 329constitute a first linear encoder serving as a detector.

Reference numeral 330 shows a flexible wiring board which sends andreceives a signal to and from the light transmitter/receiver element 329and is fixed to the first lens holding member 306 by a screw 331.

As shown in FIG. 12, the guide bar 310, the first vibration type linearactuator formed of the vibrator 319 and the slider 318, and the firstlinear encoder formed of the light transmitter/receiver element 329 andthe scale 328 are arranged along or close to a planar left side of thelight amount adjusting unit 315 (linear long side on the left whenviewed from the optical axis direction) that is one of the outersurfaces closest to the optical axis position of the light amountadjusting unit 315 of all of the outer surfaces thereof when viewed fromthe front of the optical axis direction. The first vibration type linearactuator and the first linear encoder are disposed vertically next tothe guide bar 310 to sandwich the guide bar 310.

Reference numeral 334 shows a slider which is formed of a magnet and afriction material bonded to each other and is fixed to a square frame314 c of the fourth lens holding member 314 through adhesion or thelike. Reference numeral 335 shows a vibrator which is formed of anelectromechanical energy conversion element and a plate-shaped elasticmember on which vibration is produced by the electromechanical energyconversion element. The elastic member of the vibrator 335 is made offerromagnet which is attracted by the magnet of the slider 334 to bringan press contact surface 334 a of the friction material of the slider334 into press contact with press contact surfaces 335 a (formed at twopositions in the optical axis direction as in Embodiment 1) of theelastic member of the vibrator 335.

Reference numeral 336 shows a flexible wiring board which is connectedto the electromechanical conversion element of the vibrator 335. In asecond vibration type linear actuator formed of the slider 334 and thevibrator 335, while the slider 334 is in press contact with the vibrator335, two frequency signals (pulse signals or alternate signals) indifference phases are input to the electromechanical energy conversionelement through the flexible wiring board 336 to create a substantiallyelliptic motion in the press contact surfaces 335 a of the vibrator 335to produce driving force in the optical axis direction in the presscontact surface 334 a of the slider 334.

As shown in FIG. 11, the range in which the first vibration type linearactuator is placed in the optical axis direction (the range in which theslider 318 is placed) and a movable range L2 of the second lens holdingmember 312 in the optical axis direction extend from the object side(the left in FIG. 11) of the light amount adjusting unit 315 toward theimage plane side when viewed from the direction orthogonal to theoptical axis direction. The range in which the second vibration typelinear actuator is placed in the optical axis direction (the range inwhich the slider 334 is placed) and a movable range L4 of the fourthlens holding member 314 in the optical axis direction extend from theimage plane side of the light amount adjusting unit 315 toward theobject side. In other words, the ranges in which the first and secondlinear actuators are placed (the movable ranges of the second and fourthlens holding members 312 and 314) overlap each other in the optical axisdirection.

Reference numeral 337 shows a spacer for holding the vibrator 335, 338 aplate spring for holding the spacer 337. The plate spring 338 has ashape which is not easily deformed in the in-plane direction, is easilydeformed in the direction perpendicular to the plane, and is easilydeformed in the rotation direction around an arbitrary axis included inthe plane. The plate spring 338 not easily deformed in the in-planedirection limits displacement of the vibrator 335 in the optical axisdirection (that is, the driving direction).

Reference numeral 339 shows a vibrator holding member which holds theplate spring 338 and to which the plate spring 338 is attached 6 byscrews 346 and 347. The vibrator holding member 339 is fixed to the rearbarrel 305 by screws 342 and 343.

Reference numeral 348 shows a scale which detects the position of thefourth lens holding member 314 and is fixed into a square hole 314 d inthe fourth lens holding member 314 through adhesion or the like.Reference numeral 349 shows a light transmitter/receiver element whichapplies light to the scale 348 and receives the light reflected by thescale 348 to detect the moving amount of the fourth lens holding member314. Reference numeral 350 shows a flexible wiring board which sends andreceives a signal to and from the light transmitter/receiver element 349and is fixed to the rear barrel 305 by a screw 351.

As shown in FIG. 13, the guide bar 311, the second vibration type linearactuator formed of the vibrator 335 and the slider 334, and the secondlinear encoder formed of the light transmitter/receiver element 349 andthe scale 348 are arranged along or close to a planar right side of thelight amount adjusting unit 315 (linear long side on the right whenviewed from the optical axis direction) that is one of the outersurfaces closest to the optical axis position of the light amountadjusting unit 315 of all of the outer surfaces thereof when viewed fromthe front of the optical axis direction. The second vibration typelinear actuator and the second linear encoder are disposed verticallynext to the guide bar 311 to sandwich the guide bar 311.

In addition, the set of the first vibration type linear actuator, theguide bar 310, and the first linear encoder, and the set of the secondvibration type linear actuator, the guide bar 311, and the second linearencoder are arranged substantially symmetrically with respect to an axisextending vertically through the center of the optical axis.

In the abovementioned structure, the slider 318 is formed by using themagnet which attracts the vibrator 319 to provide the press contactforce necessary for producing the driving force as the vibration typelinear actuator. Thus, any reaction force of the press contact forcedoes not act on the second lens holding member 312. As a result, thefrictional force produced at the engaging portions 312 a and 312 b ofthe second lens holding member 312 engaging with the guide bars 310 and311 is not increased and the driving load due to the friction is notincreased. In addition, the plate spring 322 produces small force, sothat the force acting from the plate spring 322 on the engaging portions312 a and 312 b engaging with the guide bars 310 and 311 is small andhardly increases the frictional force produced at the engaging portions312 a and 312 b. This enables the use of the low-power and smallvibration type linear actuator, resulting in a reduction in size of thelens barrel.

Since large press contact force does not act on the second lens holdingmember 312, the frictional force produced at the engaging portions 312 aand 312 b of the second lens holding member 312 engaging with the guidebars 310 and 311 is not increased. The power or size of the firstvibration type linear actuator does not need to be increased, and thewear due to the friction between the guide bars 310, 311 and theengaging portions 312 a, 312 b can be reduced. Also, the fine driving ofthe second lens holding member 312 (second lens unit 302) can beaccurately achieved.

Even when a manufacturing error or the like changes the position of anypress contact surface with respect to an axis in parallel with theoptical axis or the inclination around that axis in the optical axisdirection, the plate spring 322 is deformed to change the position orinclination (orientation) of the vibrator 319 to maintain both of thepress contact surfaces in parallel with each other, thereby holding anappropriate contact state between the surfaces. The plate spring 322 hasa spring constant set such that it is deformed in response to a smallerforce than the abovementioned press contact force. The press contactforce is not changed greatly even when the position or inclination ofany press contact surface is changed. Consequently, it is possible toprovide stably an output consistent with the performance inherent in thefirst vibration type linear actuator.

On the other hand, the slider 334 is formed by using the magnet whichattracts the vibrator 335 to provide the press contact force necessaryfor producing the driving force as the vibration type linear actuator.Thus, any reaction force of the press contact force does not act on thefourth lens holding member 314. As a result, the frictional forceproduced at the engaging portions 314 a and 314 b of the fourth lensholding member 314 engaging with the guide bars 311 and 310 is notincreased and the driving load due to the friction is not increased. Inaddition, the plate springs 338 produce small force, so that the forceacting from the plate springs 338 on the engaging portions 314 a and 314b engaging with the guide bars 311 and 310 is small and hardly increasesthe frictional force produced at the engaging portions 314 a and 314 b.This enables the use of the low-power and small vibration type linearactuator, resulting in a reduction in size of the lens barrel.

Since large press contact force does not act on the fourth lens holdingmember 314, the frictional force produced at the engaging portions 314 aand 314 b of the fourth lens holding member 314 engaging with the guidebars 311 and 310 is not increased. The power or size of the secondvibration type linear actuator does not need to be increased, and thewear due to the friction between the guide bars 311, 310 and theengaging portions 314 a, 314 b can be reduced. Also, the fine driving ofthe fourth lens holding member 314 (fourth lens unit 304) can beaccurately achieved.

Even when a manufacturing error or the like changes the position of anypress contact surface with respect to an axis in parallel with theoptical axis or the inclination around that axis in the optical axisdirection, the plate spring 338 is deformed to change the position orinclination (orientation) of the vibrator 335 to maintain both of thepress contact surfaces in parallel with each other, thereby holding anappropriate contact state between the surfaces. The plate spring 338 hasa spring constant set such that it is deformed in response to a smallerforce than the abovementioned press contact force. The press contactforce is not changed greatly even when the position or inclination ofany press contact surface is changed. Consequently, it is possible toprovide stably an output consistent with the performance inherent in thesecond vibration type linear actuator.

When the lens holding member is moved by a large amount, the sliderneeds to have a great length. To allow the movement of that long sliderin the optical axis direction, long space for the slider movement needsto be ensured in the optical axis direction. In Embodiment 3, however,in the first vibration type linear actuator for driving the second lensholding member 312 which is moved by a larger amount as compared withthe fourth lens holding member 314, the slider 318 having a greaterlength in the optical axis direction than that of the slider 334 of thesecond vibration type linear actuator is fixed, while the vibrator 319is moved together with the second lens holding member 312 in the opticalaxis direction. Since the long slider 318 is not moved in the opticalaxis direction in this manner, only the short space may be required forplacing the first vibration type linear actuator in the optical axisdirection, which enables a reduction in size of the lens barrel.

In Embodiment 3, in the second vibration type actuator for driving thefourth lens holding member 314 which is moved by a smaller amount ascompared with the second lens holding member 312, the slider 334 isfixed to the fourth lens holding member 314 and is moved in the opticalaxis direction, while the vibrator 335 is fixed and is not moved in theoptical axis direction. Thus, the flexible wiring board 350 does notneed to have any deformation portion, so that the flexible wiring board350 can be easily handled to enhance the flexibility in design. Thisallows a reduction in size of the lens barrel.

As described above, in Embodiment 3, the guide bar 310, the firstvibration type linear actuator, and the first linear encoder arearranged along (close to) the left side which is one of the flatsurfaces of the light amount adjusting unit 315 closest to the opticalaxis when viewed from the optical axis direction. The first vibrationtype linear actuator and the first linear encoder are disposed next tothe guide bar 310 above and below, respectively.

In addition, the guide bar 311, the second vibration type linearactuator, and the second linear encoder are arranged along (close to)the right side which is one of the flat surfaces of the light amountadjusting unit 315 closest to the optical axis when viewed from theoptical axis direction. The second vibration type linear actuator andthe second linear encoder are disposed next to the guide bar 311 aboveand below, respectively.

Thus, although the optical apparatus has the light amount adjusting unit315, the two vibration type linear actuators for driving the second andfourth lens holding members 312 and 314 (second and fourth lens units302 and 304) disposed on the object side and the image plane side of thelight amount adjusting unit 315, the two guide bars 310 and 311 forguiding the lens holding members 312 and 314 in the optical axisdirection, and the two linear encoders for detecting the positions ofthe lens holding members 312 and 314, it can be formed in a compactsize.

Since the sliders 318 and 334 are disposed next to the guide bars 310and 311, the second and fourth lens holding members 312 and 314 can bedriven smoothly. In addition, the scales 328 and 348 disposed next tothe guide bars 310 and 311 reduce displacement of the scales 328 and 348due to backlash of the engaging portions 312 a, 312 b and 314 a, and 314b of the second and forth lens holding members 312 and 314 engaging withthe guide bars 310 and 311 to enable accurate detection of positions.

When the linear actuator and the linear encoder are disposed across theoptical axis from the guide bar for guiding the lens holding memberwhich is driven and whose position is detected by them, the linearencoder may be moved in the direction opposite to the driving directionwith the guide bar as the supporting point at the start of the drivingdue to backlash at the engaging portion of the lens holding memberengaging with the guide bar. This may reduce the accuracy of theposition detection. In Embodiment 3, however, the linear actuator andthe linear encoder are disposed on the same side as the guide bar forguiding the lens holding member which is driven and whose position isdetected by them, so that such a problem does not arise and the positioncan be detected accurately.

Embodiment 4

FIGS. 15A to 19 show the structure of a lens barrel of an image-takingapparatus which is Embodiment 4 of the present invention. FIGS. 15A to15D show the lens barrel in Embodiment 4, with its exterior removed,when viewed from four directions, the right, back, left, and front,respectively. FIG. 16 shows a section view of the lens barrel inEmbodiment 4 taken along a plane in parallel with an optical axis andperpendicular to a press contact surface between a slider and a vibratorof a vibration type linear actuator. FIG. 17 shows a section view of thelens barrel in Embodiment 4 taken along a plane perpendicular to theoptical axis and perpendicular to a press contact surface of a vibrationtype linear actuator for driving a second lens unit when viewed from anobject side. FIG. 18 shows a section view of the lens barrel inEmbodiment 4 taken along a plane perpendicular to the optical axis andperpendicular to a press contact surface of a vibration type linearactuator for driving a fourth lens unit when viewed from the objectside. FIG. 19 is an exploded view showing the lens barrel in Embodiment4. FIG. 20 shows an electrical structure of the image-taking apparatusof Embodiment 4.

In FIGS. 15A to 20, in order from the object side, reference numerals401 shows a fixed first lens unit, 402 the second lens unit which ismovable in the optical axis direction for varying magnification, 415 alight amount adjusting unit, 403 a fixed third lens unit, and 404 thefourth lens unit which is movable in the optical axis direction forcorrecting image plane changes associated with varied magnification andfor focal adjustment.

Reference numeral 405 shows a rear barrel which holds an image-pickupdevice, later described, and a low pass filter (LPF), and is fixed to acamera body, not shown. Reference numeral 406 shows a first lens holdingmember which holds the first lens unit 401 and is fixed to the rearbarrel 405 by screws 407, 408, and 409.

Reference numerals 410 and 411 show guide bars (guide members) which areheld substantially in parallel with the optical axis direction by therear barrel 405 and the first lens holding member 406.

Reference numeral 412 shows a second lens holding member which holds thesecond lens unit 402 and to which a mask 432 for cutting unnecessarylight is fixed. The second lens holding member 412 engages with theguide bar 410 at an engaging portion 412 a to be guided in the opticalaxis direction and engages with the guide bar 411 at an engaging portion412 b to be prevented from rotation around the guide bar 410. Referencenumeral 413 shows a third lens holding member which holds the third lensunit 403 and is fixed to the rear barrel 405 by a screw 416. Referencenumeral 414 shows a fourth lens holding member which holds the fourthlens unit 404, and engages with the guide bar 411 at an engaging portion414 a to be guided in the optical axis direction and engages with theguide bar 410 at an engaging portion 414 b to be prevented from rotationaround the guide bar 411.

The light amount adjusting unit 415 has an outer shape which is longerin a vertical direction (first direction) than in a horizontal direction(second direction) when viewed from the optical axis direction. Thelight amount adjusting unit 415 is fixed to the rear barrel 405 by ascrew 417. The light amount adjusting unit 415 has the same structure asthat shown in FIG. 5C.

Reference numeral 418 shows a slider which is formed of a magnet and afriction material bonded to each other and is fixed into a square hole412 c in the second lens holding member 412 through adhesion or thelike.

Reference numeral 419 shows a vibrator which is formed of anelectromechanical energy conversion element and a plate-shaped elasticmember on which vibration is produced by the electromechanical energyconversion element. The elastic member of the vibrator 419 is made offerromagnet which is attracted by the magnet of the slider 418 to bringan press contact surface 418 a of the friction material of the slider418 into press contact with press contact surfaces 419 a and 419 bformed at two positions in the optical axis direction in the elasticmember of the vibrator 419.

Reference numeral 420 shows a flexible wiring board which is connectedto the vibrator 419 and transmits a signal to the electromechanicalenergy conversion element.

In a first linear actuator (vibration type linear actuator) formed ofthe slider 418 and the vibrator 419, while the slider 418 is in presscontact with the vibrator 419, two frequency signals (pulse signals oralternate signals) in difference phases are input to theelectromechanical energy conversion element through the flexible wiringboard 420 to create a substantially elliptic motion in the press contactsurfaces 419 a and 419 b of the vibrator 419 to produce driving force inthe optical axis direction in the press contact surface 418 a of theslider 418.

Reference numeral 421 shows a spacer to which the vibrator 419 is fixed,and 422 a plate spring to which the spacer 421 is fixed. The platespring 422 has a shape which is not easily deformed in the in-planedirection, is easily deformed in the direction perpendicular to theplane, and is easily deformed in the rotation direction around anarbitrary axis included in the plane. The plate spring 422 not easilydeformed in the in-plane direction limits displacement of the vibrator419 in the optical axis direction (that is, the driving direction).

Reference numeral 423 shows a vibrator frame to which the plate spring422 is fixed by screws 424 and 425. The vibrator frame 423 is fixed tothe first lens holding member 406 by screws 426 and 427.

Reference numeral 428 shows a scale which detects the position of thesecond lens holding member 412 and is fixed into a square hole 412 d inthe second lens holding member 412 through adhesion or the like.

Reference numeral 429 shows a light transmitter/receiver element whichapplies light to the scale 428 and receives the light reflected by thescale 428 to detect the moving amount of the second lens holding member412. The scale 428 and the light transmitter/receiver element 429constitute a first linear encoder serving as a detector.

Reference numeral 430 shows a flexible wiring board which sends andreceives a signal to and from the light transmitter/receiver element 429and is fixed to the first lens holding member 406 by a screw 431.

As shown in FIG. 17, the guide bar 410, the first linear actuator formedof the vibrator 419 and the slider 418, and the first linear encoderformed of the light transmitter/receiver element 429 and the scale 428are arranged along or close to a planar left side of the light amountadjusting unit 415 (linear long side on the left when viewed from theoptical axis direction) that is one of the outer surfaces closest to theoptical axis position of the light amount adjusting unit 415 of all ofthe outer surfaces thereof when viewed from the front of the opticalaxis direction. In Embodiment 4, the guide bar 410, the first linearencoder, and the first linear actuator are disposed in order from thebottom and next to each other.

Reference numeral 433 shows a coil which is fixed to the fourth lensholding member 414. Reference numeral 434 shows a flexible wiring boardfor transmitting a signal to the coil 433. The flexible wiring board 434is deformed as the fourth lens holding member 414 is moved in theoptical axis direction.

Reference numerals 435 and 436 show a magnet and a yoke, respectively.The coil 433, the magnet 435, and the yoke 436 constitute a magneticcircuit, in which the coil 433 is energized to form a second linearactuator (voice coil motor) which is an electromagnetic type linearactuator which produces driving force in the optical axis direction.Reference numeral 439 shows a yoke holding member which holds the yoke436 and is fixed to the rear barrel 405 by screws 442 and 443.

As shown in FIG. 16, the range in which the first linear actuator isplaced in the optical axis direction (the range in which the slider 418is placed) and a movable range L2 of the second lens holding member 412in the optical axis direction extend from the object side (the left inFIG. 16) of the light amount adjusting unit 415 toward the image planeside. The range in which the second linear actuator is placed in theoptical axis direction (the range in which the magnet 435 is placed) anda movable range L4 of the fourth lens holding member 414 in the opticalaxis direction extend from the image plane side of the light amountadjusting unit 415 toward the object side. In other words, the ranges inwhich the first and second linear actuators are placed (the movableranges of the second and fourth lens holding members 412 and 414)overlap each other in the optical axis direction.

Reference numeral 448 shows a scale which detects the position of thefourth lens holding member 414 and is fixed into a square hole 414 d inthe fourth lens holding member 414 through adhesion or the like.Reference numeral 449 shows a light transmitter/receiver element whichapplies light to the scale 448 and receives the light reflected by thescale 448 to detect the moving amount of the fourth lens holding member414. Reference numeral 450 shows a flexible wiring board which is usedto send and receive a signal to and from the light transmitter/receiverelement 449 and is fixed to the rear barrel 405 by a screw 451.

As shown in FIG. 18, the guide bar 411, the second linear actuatorformed of the coil 433, the magnet 435, and the yoke 436, and the secondlinear encoder formed of the light transmitter/receiver element 449 andthe scale 448 are arranged along or close to a planar right side of thelight amount adjusting unit 415 (linear long side on the right whenviewed from the optical axis direction) that is one of the outersurfaces closest to the optical axis position of the light amountadjusting unit 415 of all of the outer surfaces thereof when viewed fromthe front of the optical axis direction. In Embodiment 4, the guide bar411, the second linear actuator, and the second linear encoder aredisposed in order from the top and next to each other.

The set of the guide bar 410, the first linear actuator, and the firstlinear encoder, and the set of the guide bar 411, the second linearactuator, and the second encoder are arranged substantiallypoint-symmetrically with respect to the optical axis. To bepoint-symmetric in a strict sense, for example, the guide bar 411, thesecond linear encoder, and the second linear actuator should be disposedin this order from the top on the side of the guide bar 411, but thearrangement of Embodiment 4 may be considered to be substantiallypoint-symmetric if the guide bars, the linear actuators, and the linearencoders are seen individually. The guide bar 411 and the second linearactuator disposed next to each other as in Embodiment 4 can drive thefourth lens holding member 414 more smoothly as compared with the casewhere the guide bar 411 and the second linear actuator are disposedapart, as later described. However, a strictly point-symmetricarrangement may be used.

In FIG. 20, reference numeral 471 shows the image-pickup device formedof a CCD sensor, a CMOS sensor or the like. Reference numeral 472 showsthe vibration type linear actuator which includes the slider 418 and thevibrator 419, and serves as a driving source of the second lens unit 402(second lens holding member 412). Reference numeral 473 shows theelectromagnetic type linear actuator which is formed of the coil 433,the magnet 435, and the yoke 436, and serves as a driving source of thefourth lens unit 404 (fourth lens holding member 414).

Reference numeral 474 shows a motor which serves as a driving source ofthe light amount adjusting unit 415. Reference numeral 475 shows asecond lens encoder realized by the first linear encoder which includesthe scale 428 and the light transmitter/receiver element 429, 476 afourth lens encoder realized by the second linear encoder which includesthe scale 448 and the light transmitter/receiver element 449. Theseencoders detect the relative positions (moving amounts from a referenceposition) of the second lens unit 402 and the fourth lens unit 404 inthe optical axis direction, respectively. While Embodiment 4 employsoptical encoders as the encoders, it is possible to use a magneticencoder or an encoder which detects an absolute position by usingelectrical resistance.

Reference numeral 477 shows an aperture encoder which is, for example,of the type in which a hall element is provided within the motor 474 asthe driving source of the light amount adjusting unit 415 and is used todetect a rotational position relationship between a rotor and a statorof the motor 474.

Reference numeral 487 shows a CPU serving as a controller responsiblefor control of operation of the image-taking apparatus. Referencenumeral 478 shows a camera signal processing circuit which performsamplification, gamma correction or the like on the output from theimage-pickup device 471. After the predetermined processing, a contrastsignal of a video signal is transmitted through an AE gate 479 and an AFgate 480. The gates 479 and 480 set an optimal range in the entirescreen for extracting the signal for exposure setting and focusing.These gates 479 and 480 may have variable sizes, or a plurality of gates479 and 480 may be provided.

Reference numeral 484 shows an AF (auto-focus) signal processing circuitfor auto-focus which extracts a high-frequency component of the videosignal to produce an AF evaluation value signal. Reference numeral 485shows a zoom switch for zooming operation. Reference numeral 486 shows azoom tracking memory which stores information about target positions towhich the fourth lens unit 404 is to be driven in accordance with thecamera-to-object distance and the position of the second lens unit 402in order to maintain an in-focus state in varying magnification. Memoryin the CPU 487 may be used as the zoom tracking memory.

In the abovementioned structure, when a user operates the zoom switch485, the CPU 487 controls the vibration type linear actuator 472 fordriving the second lens unit 402 and calculates the target drivingposition of the fourth lens unit 404 based on the information in thezoom tracking memory 486 and the current position of the second lensunit 402 determined from the detection result of the second lens unitencoder 475 to control the electromagnetic type linear actuator 473 fordriving of the fourth lens unit 404 to that target driving position.Whether or not the fourth lens unit 404 has reached the target drivingposition is determined by the matching of the current position of thefourth lens unit 404 provided from the detection result of the fourthlens unit encoder 476 with the target driving position.

In the auto-focus, the CPU 487 controls the electromagnetic type linearactuator 473 to drive the fourth lens unit 404 to search for theposition where the AF evaluation value determined by the AF signalprocessing circuit 484 is at the peak.

To provide appropriate exposure, the CPU 487 controls the motor 474 ofthe light amount adjusting unit 415 to increase or reduce the aperturediameter such that the average value of the luminance signal through theAE gate 479 is equal to a predetermined value, that is, such that theoutput from the aperture encoder 477 has a value corresponding to thepredetermined value.

In the abovementioned structure, the slider 418 is formed by using themagnet which attracts the vibrator 419 to provide the press contactforce necessary for producing the driving force as the vibration typelinear actuator. Thus, any reaction force of the press contact forcedoes not act on the second lens holding member 412. As a result, thefrictional force produced at the engaging portions 412 a and 412 b ofthe second lens holding member 412 engaging with the guide bars 410 and411 is not increased and the driving load due to the friction is notincreased. In addition, the plate spring 422 produces small force, sothat the force acting from the plate spring 422 on the engaging portions412 a and 412 b engaging with the guide bars 410 and 411 is small andhardly increases the frictional force produced at the engaging portions412 a and 412 b. This enables the use of the low-power and smallvibration type linear actuator, resulting in a reduction in size of thelens barrel.

Since large press contact force does not act on the second lens holdingmember 412, the frictional force produced at the engaging portions 412 aand 412 b of the second lens holding member 412 engaging with the guidebars 410 and 411 is not increased. The power or size of the first linearactuator does not need to be increased, and the wear due to the frictionbetween the guide bars 410, 411 and the engaging portions 412 a, 412 bcan be reduced. Also, the fine driving of the second lens holding member412 (second lens unit 402) can be accurately achieved.

Even when a manufacturing error or the like changes the position of anypress contact surface with respect to an axis in parallel with theoptical axis or the inclination around that axis in the optical axisdirection, the plate spring 422 is deformed to change the position orinclination (orientation) of the vibrator 419 to maintain both of thepress contact surfaces in parallel with each other, thereby holding anappropriate contact state between the surfaces. The plate spring 422 hasa spring constant set such that it is deformed in response to a smallerforce than the abovementioned press contact force. The press contactforce is not changed greatly even when the position or inclination ofany press contact surface is changed. Consequently, it is possible toprovide stably an output consistent with the performance inherent in thefirst linear actuator.

The vibration type linear actuator is not displaced even when it is notpowered since the vibrator is always in press contact with the slider.Particularly, the second lens unit 402 is moved only in varyingmagnification and often stationary, so that the use of the vibrationtype linear actuator for driving the second lens unit can save power ascompared with the linear actuator using electromagnetic force.

On the other hand, in the linear actuator using electromagnetic force,no contact portion is provided and thus no portion is worn. Since forceis produced only in the driving direction and any lateral pressure doesnot act on the driven member (fourth lens holding member 414), anylateral pressure does not act on the engaging portions 414 a and 414 bof the driven member engaging with the guide bars 411 and 410, and theengaging portions 414 a and 414 b are hardly worn. Particularly, thefourth lens unit is moved in varying magnification and focusing, and itsmoving amount is larger than that of the second lens unit due to the AFoperation. Therefore, the electromagnetic type linear actuator is moreeffective for use in driving the fourth lens unit than the vibrationtype linear actuator in order to enhance the durability.

As described above, in Embodiment 4, the guide bar 410, the first linearactuator, and the first linear encoder are disposed next to each otheralong (close to) the left side which is one of the outer surfaces of thelight amount adjusting unit 415 closest to the optical axis positionwhen viewed from the optical axis direction. The guide bar 411, thesecond linear actuator, and the second linear encoder are disposed nextto each other along (close to) the right side which is one of the outersurfaces of the light amount adjusting unit 415 closest to the opticalaxis position when viewed from the optical axis direction. Thus,although the optical apparatus has the light amount adjusting unit 415,the two linear actuators for driving the second and fourth lens holdingmembers 412 and 414 (second and fourth lens units 402 and 404) disposedon the object side and the image plane side of the light amountadjusting unit 415, the two guide bars 410 and 411 for guiding the lensholding members 412 and 414 in the optical axis direction, and the twolinear encoders for detecting the positions of the lens holding members412 and 414, it can be formed in a compact size.

The scale 428 of the first linear encoder disposed next to the guide bar410 reduces displacement of the scale 428 due to backlash of theengaging portions 412 a and 412 b of the second lens holding member 412engaging with the guide bars 410 and 411 to enable accurate detection ofpositions.

When the linear actuator and the linear encoder are disposed across theoptical axis from the guide bar for guiding the lens holding memberwhich is driven and whose position is detected by them, the linearencoder may be moved in the direction opposite to the driving directionwith the guide bar as the supporting point at the start of the drivingdue to backlash at the engaging portion of the lens holding memberengaging with the guide bar. This may reduce the accuracy of theposition detection. In Embodiment 4, however, the linear actuator andthe linear encoder are disposed on the same side as the guide bar forguiding the lens holding member which is driven and whose position isdetected by them, so that such a problem does not arise and the positioncan be detected accurately.

In addition, since the second linear actuator is disposed next to theguide bar 411, the fourth lens holding member 414 can be drivensmoothly.

According to each of Embodiments 1 to 4, the linear actuator, the guidemember, and the detector are placed along the outer surface in thesecond direction of the light amount adjusting unit which has the shapeelongated in the first direction. In other words, they are arranged byeffectively using the space provided outside the light amount adjustingunit in the second direction shorter than the first direction. They canbe arranged compactly to reduce the size of the optical apparatus.

It is possible to achieve the balanced arrangement of the set of thelinear actuator, the guide member, and the detector associated with thefirst lens and the set of the linear actuator, the guide member, and thedetector associated with the second lens in the second direction,thereby realizing the small optical apparatus even it has the two setsof the linear actuators, the guide member, and the detectors. Especiallywhen the vibration type linear actuator is used as at least one of thetwo linear actuators, the optical apparatus can be further reduced insize as compared with the case where the electromagnetic type linearactuator is used for both of the two linear actuators.

The preferred embodiments of the present invention have been described.However, the present invention is not limited to the structuresdescribed in Embodiments 1 to 4, and various modifications may be madein each of Embodiments 1 to 4.

While each of Embodiments 1 to 4 has been described in conjunction withthe image-taking apparatus integral with the lens, the present inventionis applicable to an interchangeable lens (optical apparatus) which isremovably mounted on an image-taking apparatus body. The presentinvention is applicable not only to the image-taking apparatus, but alsoto various optical apparatuses for driving a lens by a linear actuator.

While each of Embodiments 1 to 4 has been described in conjunction withthe holding mechanism which holds the vibrator and the slider atvariable positions and inclinations, it is possible to provide a holdingmechanism which allows one of the position and inclination to bevariable.

This application claims a foreign priority benefit based on JapanesePatent Application No. 2005-125750, filed on Apr. 22, 2005, which ishereby incorporated by reference herein in its entirety as if fully setforth herein.

1. An optical apparatus comprising: a light amount adjusting unit whichadjusts a light amount by a pair of light shield members translating ina first direction orthogonal to an optical axis direction; a lens; avibration type linear actuator which drives the lens in the optical axisdirection with vibration produced through an electromechanical energyconversion action; a guide member which guides the lens in the opticalaxis direction; and a detector which detects the position of the lens,wherein, when viewed from the optical axis direction of the opticalapparatus, the vibration type linear actuator, the guide member, and thedetector are arranged along an outer surface of the light amountadjusting unit, the outer surface being provided in a second directionorthogonal to the first direction.
 2. The optical apparatus according toclaim 1, wherein the lens includes a first lens disposed closer to anobject than the light amount adjusting unit and a second lens disposedcloser to an image plane than the light amount adjusting unit, thevibration type linear actuator includes a first vibration type linearactuator and a second vibration type linear actuator which drive thefirst and second lenses in the optical axis direction, respectively, theguide member includes a first guide member and a second guide memberwhich guide the first and second lenses in the optical axis direction,respectively, the detector includes a first detector and a seconddetector which detect the positions of the first and second lenses,respectively, and wherein, when viewed from the optical axis directionof the optical apparatus, the first vibration type linear actuator, thefirst guide member, and the first detector are arranged along a firstouter surface of the light amount adjusting unit, the first outersurface being provided in the second direction, and the second vibrationtype linear actuator, the second guide member, and the second detectorare arranged along a second outer surface, the second outer surfacebeing provided on the opposite side to the first outer surface of thelight amount adjusting unit.
 3. The optical apparatus according to claim2, wherein, when viewed from the optical axis direction of the opticalapparatus, the first and second vibration type linear actuators aredisposed in ranges which overlap each other at least partially in theoptical axis direction.
 4. The optical apparatus according to claim 2,wherein, when viewed from the optical axis direction of the opticalapparatus, the set of the first vibration type linear actuator, thefirst guide member, and the first detector, and the set of the secondvibration type linear actuator, the second guide member, and the seconddetector are arranged symmetrically with respect to an axis extending inthe first direction through the optical axis.
 5. The optical apparatusaccording to claim 2, wherein, when viewed from the optical axisdirection of the optical apparatus, the set of the first vibration typelinear actuator, the first guide member, and the first detector, and theset of the second vibration type linear actuator, the second guidemember, and the second detector are arranged point-symmetrically withrespect to the optical axis.
 6. An optical apparatus comprising: a lightamount adjusting unit which adjusts a light amount by a pair of lightshield members translating in a first direction orthogonal to an opticalaxis direction; a first lens disposed closer to an object than the lightamount adjusting unit; a second lens disposed closer to an image planethan the light amount adjusting unit; a first linear actuator whichdrives the first lens in the optical axis direction; a second linearactuator which drives the second lens in the optical axis direction; afirst guide member and a second guide member which guide the first andsecond lenses in the optical axis direction, respectively; and a firstdetector and a second detector which detect the positions of the firstand second lenses, respectively, wherein, when viewed from the opticalaxis direction of the optical apparatus, the first linear actuator, thefirst guide member, and the first detector are arranged along a firstouter surface of the light amount adjusting unit, the first outersurface being provided in a second direction orthogonal to the firstdirection, and the second linear actuator, the second guide member, andthe second detector are arranged along a second outer surface of thelight amount adjusting unit, the second outer surface being provided onthe opposite side to the first outer surface.
 7. The optical apparatusaccording to claim 6, wherein, when viewed from the optical axisdirection of the optical apparatus, the first and second linearactuators are disposed in ranges which overlap each other at leastpartially in the optical axis direction.
 8. The optical apparatusaccording to claim 6, wherein, when viewed from the optical axisdirection of the optical apparatus, the set of the first linearactuator, the first guide member, and the first detector, and the set ofthe second linear actuator, the second guide member, and the seconddetector are arranged symmetrically with respect to an axis extending inthe first direction through the optical axis.
 9. The optical apparatusaccording to claim 6, wherein, when viewed from the optical axisdirection of the optical apparatus, the set of the first linearactuator, the first guide member, and the first detector, and the set ofthe second linear actuator, the second guide member, and the seconddetector are arranged point-symmetrically with respect to the opticalaxis.
 10. The optical apparatus according to claim 6, wherein at leastone of the first and second linear actuators is a vibration typeactuator which produces driving force with vibration produced through anelectromechanical energy conversion action.